you can make your own thinner,,,,,,,a gallon costs about the same as one bottle of Testor's does
I don't recommend trying this until you have tried the Testor's brand stuff though, because you won't know if you are "doing better or worse" until you have a baseline.
mix 3 pints of distilled water with 3 pints of windshield washer fluid, then add drops of Liquitex Flow Aid* and Liquitex Slow Dry* to that mixture, add 1 pint of either ArmorAll Auto Glass cleaner or Clorox Green Works Natural Glass Cleaner (I use the Blue kind, lol),,,,,,,,add Pledge (Future) to the jug until you top off and have one gallon.
Turn this over and over a bunch of times to get it all mixed up, then let it settle before you use it the first time (to get rid of the bubbles)
I modified this from another guy's formula,,,,,and this works for Polly Scale, Aeromaster, and Model Master paints.
You still need to keep a cotton swab wet with cleaner nearby for tip-dry as you spray, but, you will use it far less often.
hope someone finds this helpful
Rex (the Polly Scale Rebel)
*"add drops" means to follow their label instructions, you want some of each in there, but, you don't want to go too far, you can start out with 10 drops of each, and add more if you want to,,,,,,,,other companies' products will also work for these if you choose